 (vec "123")
 (apply map vector [[1 2 3] [4 5 6] [7 8]])
 
+;add a pre to your function
+
+(defn try-pre
+  [x]
+  {:pre [(pos? x)]}
+  (+ x 2))
+
+;(try-pre -2)
+(try-pre 2)
 
 
+

(ns language.protocol)


(defprotocol Matrix
  "Protocol for working with 2d data structures"
  (lookup [matrix i j])

        (apply map vector vov))
  (dims [vov]
        [(count vov) (count (first vov))])
  nil
  (lookup [x i j])
  (update [x i j val])
